- Add support for media channels.
    - Add :class:`MediaChannel`.
        - Unless otherwise noted, media channels behave just like forum channels.
    - Add :attr:`ChannelType.media`.
    - Add :attr:`CategoryChannel.media_channels`, :attr:`Guild.media_channels`.
    - Add :attr:`CategoryChannel.create_media_channel`, :attr:`Guild.create_media_channel`.
    - Add :attr:`ChannelFlags.hide_media_download_options`.
